If you do not have shower facilities, a reasonable proxy is to wait until you've stopped sweating (usually 10 min. post-ride) and clean up with unscented baby wipes in the bathroom (and if needed, use a travel bottle of shampoo to rinse sweat out of your hair). The rule is try not to pack what you can leave at your destination (towels, clothes)

Most bike commuters I know bring batches of clothes to the office and/or wear sweat-wicking business casual (Nike's golf apparel or cheaper). Hopefully you might be able to store a suit/pants with a colleague? They discuss and dissect bike commuting on Bike Forums endlessly. http://www.bikeforums.net/forumdisplay.php?f=20